1. Field of the Invention
The present invention relates to an airbag that is used as a knee airbag, or the like, housed below an instrument panel.
2. Related Technology
A knee airbag is an occupant restraint system which is inflated and deployed near the occupant's knee region upon the occurrence of an automobile accident. As a result of deployment of a knee airbag, it is possible to prevent the occupant's knee region from colliding with the instrument panel or the like.
A knee airbag is mainly housed below the instrument panel; for instance, inside the lower part of the steering column cover in the case of the driver seat. In order to enable the mounting thereof in a limited housing space, a knee airbag is mounted in a state of being folded or wound into a compact size. Moreover, in the event of an accident, the knee airbag receives the supply of gas from an inflator (gas generator) and is inflated and deployed toward the inside of the occupant compartment of the vehicle.
The knee airbag needs to be inflated and deployed in the space defined from below the instrument panel to the occupant's knee region. Since this space is extremely small, it is not possible to prevent the knee region from colliding with the instrument panel unless the knee airbag is inflated and deployed quickly. Thus, the knee airbag is devised in terms of the folding method and the smooth inflow of gas in order to achieve instantaneous deployment.
For example, Japanese Patent Application Publication No. 2004-330959 discloses a passenger seat airbag device with a knee region protection bag internally comprising an inflator that is inserted into a substantially cylindrical diffuser (rectifier). According to this document, first to third rectifying openings having different opening areas are formed in the diffuser, and, by using such first to third rectifying openings, the knee region protection bag can be deployed ahead of the head/chest protection bag.
With the technology described in Japanese Patent Application Publication No. 2004-330959, the tubular diffuser is long and overlaps with the insertion hole of the inflator. Accordingly, a hole is formed in the diffuser at the position which overlaps with the insertion hole, and the inflator that is inserted from the outside to the inside through the insertion hole was directly guided and inserted into the diffuser. Nevertheless, the outlet of both ends of the long diffuser becomes blocked due to the folding of the airbag during the housing thereof, resulting in a so-called choking where gas cannot be smoothly discharged from both ends of the tubular diffuser during the inflation and deployment of the airbag occurred.
Thus, one consideration may be shortening the diffuser. Consequently, while the diffuser will no longer overlap with the insertion hole and be positioned slightly separated from the insertion hole, a need arises for moving the tip of the inserted inflator to the end of the tubular diffuser upon the insertion thereof. Here, there is a possibility that the inflator is erroneously deviated outside the tubes of the diffuser.